| """Produces a browser-playable preview copy of a retained sample, cached on |
| first request. |
| |
| Two independent problems, confirmed directly on real files: |
| 1. Reference clips arrive from the validator with the moov atom at the end |
| of the file (not faststart) -- a 265MB file needs its tail fetched and |
| parsed before a browser can even start playback. |
| 2. Compressed outputs are frequently HEVC, which Chrome/Firefox cannot |
| decode in <video> on most platforms (licensing) -- codec-incompatible, |
| not a streaming problem, and looks identical to (1) from the UI (an |
| endless spinner). |
| |
| Preview copies are always H.264 + faststart, scaled down (this is a visual |
| check, not a quality measurement -- the real score already covers that), |
| and cached so only the first view per item pays the transcode cost. |
| """ |
| from __future__ import annotations |
|
|
| import subprocess |
| from pathlib import Path |
|
|
| PREVIEW_CACHE_DIR = Path("/root/vidaio-cms/web-preview") |
| PREVIEW_MAX_WIDTH = 1280 |
| TRANSCODE_TIMEOUT_SECONDS = 90 |
|
|
|
|
| def get_preview(source_path: Path, cache_key: str) -> Path | None: |
| PREVIEW_CACHE_DIR.mkdir(parents=True, exist_ok=True) |
| cached = PREVIEW_CACHE_DIR / f"{cache_key}.mp4" |
| if cached.exists() and cached.stat().st_mtime >= source_path.stat().st_mtime: |
| return cached |
|
|
| tmp = PREVIEW_CACHE_DIR / f"{cache_key}.tmp.mp4" |
| try: |
| subprocess.run( |
| [ |
| "ffmpeg", "-y", "-i", str(source_path), |
| "-map", "0:v:0", |
| "-c:v", "libx264", "-preset", "veryfast", "-crf", "26", |
| "-vf", f"scale='min({PREVIEW_MAX_WIDTH},iw)':-2", |
| "-movflags", "+faststart", |
| "-an", |
| str(tmp), |
| ], |
| capture_output=True, timeout=TRANSCODE_TIMEOUT_SECONDS, check=True, |
| ) |
| except (subprocess.CalledProcessError, subprocess.TimeoutExpired, FileNotFoundError): |
| tmp.unlink(missing_ok=True) |
| return None |
|
|
| tmp.rename(cached) |
| return cached |
|
|
